This invention relates to frictional type fasteners for joints including joint members of wood, metal, plastic or combinations thereof and, more particularly, to a dowel type fastener intended for compressive insertion within a recess, aperture or bore for frictionally engaging the sides of the recess, aperture or bore to hold the joint member to another member.
Dowel type fasteners for wood and other type joints are well-known. In the past, such dowel fasteners have either been solid and used for alignment purposes in conjunction with adhered or glued joints or have been slotted, solid or tubular dowels which frictionally engage the inside surfaces of bores or apertures in the joint members in which they are inserted. Although certain of the prior known slotted dowels or pins have included spiral or helical slots, the vast majority have included rectilinear slots. Such rectilinearly slotted dowels are less than satisfactory for furniture or other joints because, if inserted in a slot or elongated aperture, it is possible that the slot area of the circumference of such dowel could engage the side of the slot or aperture and produce a loose fit and less than satisfactory frictional holding power.
With respect to prior spiral or helically slotted dowels, they too have been less than satisfactory because of difficulty in inserting such dowels between joint members. Such dowels have been stiff and inflexible, due in part to the material thickness necessary for their strength.
In order to overcome insertion difficulties, certain prior, rectilinearly or saw-tooth slotted dowel fasteners have included tapered ends provided by either shearing their end surfaces or forming over the entire end surface of such dowel. In either case, the taper was insufficient to allow proper insertion of the relatively stiff dowel into two holes which might be slightly out of alignment in opposing joint members or sufficiently small to obtain a proper frictional hold in softer materials. In addition, such tapered ends on prior known dowels have tended to collapse when struck for insertion of the opposite end in a joint structure eliminating the ability to insert the collapsed end into its respective joint member. On the other hand, if the taper was sufficiently reduced to avoid such collapse, the aperture or bore size with which the stiff, slotted dowel could be used was severly limited.
Apart from the above, another common problem was the frequent insertion of slotted, dowel type fasteners in holes or apertures which were undersized. This caused complete closure of the slot in the dowel and/or over-compression and collapse of the dowel diameter itself or splitting of the joint member because of the small size into which the dowel was forced. The only way to prevent such collapse or deformation was to carefully regulate the bore size into which the dowel was fitted. The prior known dowels had no structure to prevent such insertion.
In addition to the above, a need was apparent in the fastener industry for a dowel fastener which could offer various levels of holding power, provide consistent frictional engagement force, be sufficiently flexible and resilient to allow insertion in varying hole or aperture sizes, allow insertion in slightly nonaligned or nonconcentric holes or apertures, and yet prevent insertion in holes or apertures which were undersized and would cause plastic deformation or failure of the dowel.